Improved method of producing a liquid tobacco extract

ABSTRACT

A method of producing a liquid tobacco extract, the method including the steps of: preparing a tobacco material; applying an alkaline solution to the tobacco material to produce an alkalised tobacco material; heating the alkalised tobacco material at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 30 minutes, the alkalised tobacco material being heated in a flow of inert gas or in a flow of a combination of an inert gas with water or steam, and a water content of the alkalised tobacco material, prior to the heating step, being between 10 percent by weight and 20 percent by weight; condensing volatile compounds released from the alkalised tobacco material during the heating step and collecting condensate of the volatile compounds; and forming a liquid tobacco extract comprising the condensate of the volatile compounds.

The invention relates to a method of producing a liquid tobacco extractand to a liquid tobacco extract produced by such a method.

Aerosol-generating systems for delivering an aerosol to a user thatcomprise an atomiser configured to generate an inhalable aerosol from aliquid formulation, such as a liquid nicotine formulation, are known.Some known aerosol-generating systems comprise a thermal atomiser suchas an electric heater that is configured to heat and vaporise the liquidformulation to generate an aerosol. One popular type of electricallyheated aerosol-generating system is an e-cigarette. Other knownaerosol-generating systems comprise a non-thermal atomiser that isconfigured to generate an aerosol from the liquid formulation using, forexample, impinging jet, ultrasonic or vibrating mesh technologies.

Several methods for producing liquid tobacco extracts from tobaccomaterial are known. Liquid tobacco extracts may be produced by a hightemperature extraction process in which nicotine and other volatileflavour compounds are extracted from tobacco material and collected in asuitable solvent to form a natural liquid tobacco extract.

Maceration methods are also known, wherein a tobacco material is kept insuspension in an extraction liquid for a period of up to several weeksor even months. The resulting slurry is subsequently filtered, and theliquid phase thus collected can be used to manufacture a vaporisableliquid formulation. In one such method—so-called “cold macerationmethod”—there is generally no way of controlling the extractionconditions (e.g. temperature and pressure). In a variant of a macerationmethod, which has been described for example in US 2012/192880, theslurry is heated to 100 degrees Celsius or more.

The liquid phase collected upon filtration of the slurry, whichrepresents the primary product of a maceration process, is highlydiluted, and tends to have a low content of apolar tobacco flavourspecies. Additionally, the liquid phase typically contains little to nonicotine. As such, liquid extracts obtained by a maceration methodgenerally need to be supplemented with additional ingredients, such asnicotine salts and glycerin, before being used in a vaporisable liquidformulation.

Alternative processes are known, wherein a tobacco material issubstantially boiled in water for a period of hours or even days to forma vapour phase, and a distillate obtained by condensation of the vapourphase is continuously collected in a vessel. Over time, an oily, waxylayer containing a high proportion of apolar compounds builds up on thesurface of the distillate.

On the one hand, the aqueous portion, above which the waxy layer buildsup, and which contains nicotine and other water-soluble compounds, isrecycled to the boiler. An apolar co-solvent may optionally be fed intothe boiler with the aqueous portion in order to increase the extractionyield. On the other hand, the waxy phase is collected and ultimatelyforms the primary product of one such hydro-distillation process. Suchproduct is often referred to as “tobacco essential oil”, and contains ahigh proportion of apolar compounds found in tobacco, such as fattyacids, neophytadiene, etc. The tobacco essential oil obtained by onesuch method typically contains no nicotine.

It is also known to subject tobacco material to an extraction processinvolving use of a volatile apolar solvent. Examples of suitablesolvents are cyclic or acyclic short alkanes, as well as chlorinatedsolvents like dichloromethane. In one such process, the excess solventmay be evaporated by controlled heating under vacuum. Typically, this isdone in the presence of ethanol, which has a higher boiling point thanthe extraction solvent, such that even traces of the extraction solventcan be detected.

The primary product of one such solvent-aided extraction process isoften referred to as “tobacco absolute”, and may contain traces ofethanol. It is a waxy product and contains a highly concentrated mixtureof most of the apolar compounds that can be extracted with the specificsolvent, generally including nicotine, which is generally present atrelatively high concentrations.

An alternative extraction process involves contacting a tobacco materialwith a solvent under supercritical conditions, such as supercriticalcarbon dioxide. One such process is disclosed in US 2013/160777, andrelies on the principle that volatile substances within a feed materialcontacted with a supercritical fluid may partition into thesupercritical phase. After dissolution of any soluble material, thesupercritical fluid containing the dissolved substances can be removed,and the dissolved components of the feed matter can be separated outfrom the supercritical fluid. The primary product of a supercriticalextraction process is substantially similar to the “tobacco absolute” ofa solvent-aided extraction process run at lower temperature andpressure, contains no residual solvent and typically has a high level ofthe waxy, apolar compounds and includes nicotine, which is generallypresent at relatively high concentrations.

However, all the tobacco extracts obtainable by methods known in the arttend to have a very low level—if any—of compounds associated with theflavour of heated tobacco, such as furaneol.

In general, as discussed above, liquid tobacco extracts obtained by suchknown extraction processes may have a low level of nicotine. Further,liquid tobacco extracts obtained by such extraction processes may have alow level and low variety of flavour species. Liquid tobacco extractsobtained by such extraction processes may also have a high level ofundesirable compounds. In general, the concentration of nicotine,flavour species and undesirable compounds obtained by such extractionprocesses may be significantly impacted by the type or types of tobaccoused as a starting material.

A purpose of the invention is to alleviate one or more of the drawbacksof the liquid tobacco extracts obtained by known processes. Inparticular, it would be desirable to provide a method for the productionof a novel and improved liquid tobacco extract. It would be particularlydesirable to provide such a method for producing such a liquid tobaccoextract that could be carried out more efficiently than existingprocesses.

The present disclosure relates to a method for producing a liquidtobacco extract from a tobacco material. The method may include the stepof preparing a tobacco material. An alkaline solution may be applied tothe tobacco material to produce an alkalised tobacco material. Thealkalised tobacco material may be heated at an extraction temperature ofbetween about 100 degree Celsius and about 160 degrees Celsius. Theheating may be carried out for at least 30 minutes. The alkalisedtobacco material may be heated in a flow of inert gas or in a flow of acombination of an inert gas with water or steam. The method may furthercomprise the step of condensing the volatile compounds released from thealkalised tobacco material during the heating step and collecting thecondensate of the volatile compounds. The method may further comprisethe step of forming a liquid tobacco extract comprising the condensateof the volatile compounds.

The present disclosure further relates to an alternative method ofproducing a liquid tobacco extract from a tobacco material. The methodmay include the step of preparing a tobacco material. The tobaccomaterial may be heated at an extraction temperature of between 100degrees Celsius and 160 degrees Celsius for at least 90 minutes. Themethod may further comprise the steps of collecting the volatilecompounds released from the tobacco starting material during the heatingstep and forming a first liquid tobacco extract comprising the collectedvolatile compounds from the tobacco starting material. The method mayfurther comprise the step of applying an alkaline solution to theresidual tobacco material from the heating step to produce an alkalisedtobacco material. The alkalised tobacco material may be heated at anextraction temperature of between 100 degrees Celsius and 160 degreesCelsius. The method may further comprise the steps of collecting thevolatile compounds released from the alkalised tobacco material duringthe heating step and forming a second liquid tobacco extract comprisingthe collected volatile compounds from the alkalised tobacco material.

According to a first aspect of the present invention there is provided amethod of producing a liquid tobacco extract, the method comprising thesteps of: preparing a tobacco material; applying an alkaline solution tothe tobacco starting material to produce an alkalised tobacco material;heating the alkalised tobacco material at an extraction temperature ofbetween about 100 degrees Celsius and about 160 degrees Celsius for atleast about 30 minutes, wherein the alkalised tobacco material is heatedin a flow of inert gas or in a flow of a combination of an inert gaswith water or steam; condensing the volatile compounds released from thealkalised tobacco material during the heating step and collecting thecondensate of the volatile compounds; and forming a liquid tobaccoextract comprising the condensate of the volatile compounds.

According to a second aspect of the present invention there is provideda method of producing a liquid tobacco extract, the method comprisingthe steps of: preparing a tobacco material; heating the tobacco materialat an extraction temperature of between 100 degrees Celsius and 160degrees Celsius for at least 90 minutes; collecting the volatilecompounds released from the tobacco starting material during the heatingstep; forming a first liquid tobacco extract comprising the collectedvolatile compounds from the tobacco starting material; applying analkaline solution to the residual tobacco material from the heating stepto produce an alkalised tobacco material; heating the alkalised tobaccomaterial in an extraction chamber at an extraction temperature ofbetween 100 degrees Celsius and 160 degrees Celsius; collecting thevolatile compounds released from the alkalised tobacco material duringthe heating step; and forming a second liquid tobacco extract comprisingthe collected volatile compounds from the alkalised tobacco material.

According to the present invention there is further provided a liquidtobacco extract produced by the methods of the present invention, asdefined above.

As used herein with reference to the invention, the term “liquid tobaccoextract” describes the direct product of an extraction process carriedout on a tobacco material. Thus, the tobacco extract typically includesa mixture of natural components separated from, removed from, or derivedfrom, a natural tobacco material using tobacco extraction processingconditions and techniques. Thus, in one such process extracted tobaccocomponents are removed from the natural tobacco material and separatedfrom unextracted tobacco components. According to the present invention,the extraction process for producing the liquid tobacco extractcomprises heating the tobacco material under specific heating conditionsand collecting the volatile compounds generated. The liquid tobaccoextract therefore consists of the mixture of natural tobacco componentsthat have derived from the tobacco material and have been extracted orformed during the extraction process, typically in combination with oneor more materials other than the tobacco material, such as a non-aqueousextraction solvent used during the extraction process. As will bedescribed in more detail below, the volatile compounds released from thestarting tobacco material may be collected using an absorption techniquein which the volatile compounds are trapped in a non-aqueous extractionsolvent. By way of example, an inert gas flow containing the volatilecompounds may be directed into a container of a non-aqueous extractionsolvent. The non-aqueous extraction solvent is preferably an aerosolformer.

The present invention provides novel extraction methods including analkaline treatment step during which an alkaline solution is applied tothe tobacco material. In accordance with the first aspect of theinvention, the alkaline treatment step may be carried out on the tobaccomaterial prior to the heating step. The inclusion of an alkalinetreatment step prior to heating, in combination with the definedconditions for heating, has been found to provide a very significantincrease in the yield of nicotine. For example, the inclusion of thealkaline treatment step has been found in certain cases to provide anincrease of up to 900 percent in the extraction yield of nicotinecompared to an equivalent extraction carried out without the alkalinetreatment step. The inclusion of the alkaline treatment step prior toheating has also been found to bring about a favourable change in thebalance of flavour compounds in the resultant extract. In particular,the yield of certain desirable flavour compounds, such as certainpyrazine compounds, may be improved. Advantageously, these increases inthe yield of nicotine and other flavour compounds is provided withoutany increase in the yield of TSNAs. Overall, the ratios of desirable toundesirable compounds in the extract can therefore be increased.

Without wishing to be bound by theory, it is believed that the alkalinetreatment of the tobacco material facilitates the transition of nicotinefrom a protonated form to a free-base form, which in turn helps totransfer the nicotine into the gas phase more efficiently during theheating step.

In alternative methods according to the second aspect of the invention,the alkaline treatment step is carried out on the residual tobaccomaterial that remains after the heating step. The alkalised tobaccomaterial is then subjected to a second heating step to extract furthervolatile compounds which may optionally be added to the volatilecompounds collected from the first heating step. Such methods thereforeinvolve two separate heating steps to be carried out on the same batchor sample of tobacco material.

The “residual tobacco material” refers to the tobacco material that isleft behind after the extraction that is carried out during the firstheating step as defined above, in which the tobacco material is heatedto a temperature of between 100 degrees and 160 degrees. The residualtobacco material is therefore the same tobacco material as used in theheating step, but which has had a proportion of volatile compoundsremoved from it already as a result of the extraction.

The inclusion of the alkaline treatment step at this stage in theextraction method, after the first heating step, has been found tofurther optimise the composition of the liquid tobacco extract that canbe produced by the extraction method. The alkaline treatment of theresidual tobacco material prior to a second extraction enables thesecond heating step to extract a higher proportion of the nicotine fromthe tobacco material such that the overall level of nicotine extractedcan be maximised. This is for the same reasons as described above inrelation to other embodiments of the invention.

The extraction of the additional nicotine is carried out in a separate,subsequent step to the first extraction of volatile compounds, so thatthe first extraction is unaffected by the alkaline treatment step. Thisallows the first extraction to be optimised in relation to the yield ofthe desirable flavour compounds from the tobacco material, whilst thesecond extraction advantageously enhances the overall nicotine yield.

The alkaline treatment step can advantageously be carried out within theexisting extraction apparatus, so that the overall impact of thealkaline treatment step on the efficiency of the extraction process canbe minimised. The alkaline treatment step can be carried out withreadily available apparatus, which can be incorporated into existingextraction apparatus without the need for significant modification.

In addition to providing an improved yield of nicotine as a result ofthe inclusion of the alkaline treatment step, the extraction method ofthe present invention uses specific extraction conditions toadvantageously provide an improved liquid tobacco extract having asignificantly improved balance of desirable compounds to undesirablecompounds. In particular, the extraction method of the present inventionprovides a liquid tobacco extract having a maximised ratio of desirablecompounds to undesirable compounds for the tobacco material. Forexample, the use of the specific combination of extraction temperatureand time as defined enables the levels of nicotine compounds to beoptimised whilst also minimising the levels of undesirable compoundssuch as furans, carbonyls, phenols and TSNAs.

The inventors of the present invention have found that, in contrast tothe existing extraction processes that have been discussed above,methods in accordance with the present invention advantageously providea liquid tobacco extract that has a significantly higher content ofcompounds associated with the flavour of heated tobacco, such as forexample furaneol. These compounds are substantially absent, or arepresent in trace amounts, in a tobacco extract obtained by a macerationprocess, which also typically contains little to no nicotine. Thesecompounds are also generally absent or present in trace amounts in atobacco extract obtained using a solvent, including under supercriticalconditions. Similarly, a tobacco essential oil obtained by way of adistillation process also typically has a very low content—if any—ofsuch compounds associated with the flavour of heated tobacco.

The liquid tobacco extracts obtained by methods in accordance with theinvention present significant compositional differences with respect totobacco extracts obtained by the existing extraction processes, and canbe used as an e-liquid or for the preparation of an e-liquid that, whenheated, generates an aerosol having a distinct composition and flavourcharacteristics compared with currently available e-liquids. Inparticular, liquid tobacco extracts obtained by a method in accordancewith the invention may be used to generate an aerosol that provides aheated tobacco taste which more closely resembles an aerosol generatedby conventional cigarettes or upon heating tobacco in a heat-not-burndevice relative to available aerosols produced from existing liquidnicotine compositions.

The extraction method of the present invention enables a liquid tobaccoextract to be produced which has optimised levels of nicotine andflavour compounds without the need for addition of such compounds afterextraction. The resultant liquid tobacco extract can thereforeadvantageously be used directly to provide a nicotine composition. Theresultant liquid tobacco extract can also be modified by one or morefurther processing steps or mixed with one or more further ingredientsto form a nicotine composition. The nicotine composition can be for usein an e-cigarette or other aerosol-generating system.

Aerosol-generating systems for delivering an aerosol to a user thatcomprise an atomiser configured to generate an inhalable aerosol from aliquid formulation, such as a liquid nicotine composition, are known, asdescribed above.

The method of producing a liquid tobacco extract of the presentinvention can be used effectively for all types and grades of tobacco,including Burley tobacco, flue-cured tobacco and Oriental tobacco. Themethod steps can be readily adjusted in order to provide a consistentliquid tobacco extract for a variety of blends of tobacco type. Theextraction method is additionally suitable for a variety of forms oftobacco material.

As described above, the methods of the present invention incorporate analkaline treatment step, which is carried out on the tobacco materialprior to heating, or on the residual tobacco material. In either case,the alkaline treatment step may be carried out in the same way and anyreference below to alkaline treatment of the tobacco material should beconsidered to also apply to alkaline treatment of the residual tobaccomaterial, unless stated otherwise.

The alkaline treatment is carried out by applying an alkaline solutionto the tobacco material to produce an alkalised tobacco material.Preferably, the alkaline solution is sprayed onto the tobacco material,such that the alkaline solution can be distributed as evenly as possiblethroughout the tobacco material.

In methods according to the first aspect of the invention, the alkalinesolution may be applied to the tobacco material within the extractionchamber that the heating step is carried out in, or within a different,separate apparatus.

In methods according to the second aspect of the invention where thealkaline treatment step is carried out on the residual tobacco materialfrom the first heating step, the alkaline solution may be applied to theresidual tobacco material within the extraction chamber that the firstheating step has taken place in. Alternatively, the residual tobaccomaterial may be collected from the extraction chamber that the firstheating step has taken place in and the alkaline solution may be appliedto the residual tobacco material within a different apparatus.Alternatively again, the alkaline solution may be applied to theresidual tobacco material as it is transferred from a first extractionchamber within which the first heating step takes place, to a secondextraction chamber within which the second heating step takes place.

Preferably, the tobacco material is continuously circulated or agitatedduring application of the alkaline solution, so that there is ahomogenous distribution of the alkaline solution. This optimises theeffect of the alkaline solution on the nicotine yield from the alkalisedtobacco material.

Preferably, the pH of the alkalised tobacco material is at least about8.5, more preferably at least about 9.0, more preferably at least about9.5. Preferably, the pH of the alkalised tobacco material is no morethan 11.

The “pH of the alkalised tobacco material” refers to the pH of anaqueous suspension of the alkalised tobacco material which is formed bymaking a suspension of the alkalised tobacco material in water at aratio of 1:20. The pH of the suspension is measured after 30 minutessoaking time.

As described above, in the alkaline treatment step, an alkaline solutionis applied to the tobacco material, or residual tobacco material. Asuitable alkaline solution may be selected, for example, depending onthe desired pH of the tobacco material. Preferably, the alkalinesolution is an aqueous solution of an alkali agent. A preferred exampleof a suitable alkaline solution for the alkaline treatment step is anaqueous solution of potassium carbonate. Other suitable alkalinesolutions for use in the present invention include but are not limitedto sodium hydroxide, sodium carbonate and hydrogen peroxide.

Preferably, the water content of the alkalised tobacco material, priorto the heating step, is between about 10 percent by weight and about 20percent by weight, more preferably between about 12 percent and about 20percent by weight, more preferably between about 12 percent and about 18percent by weight. By providing an alkalised tobacco material having awater content within this preferred range, the extraction of volatilecompounds during the subsequent heating step has been found to beoptimised. Preferably, the desired water content of the alkalisedtobacco material is provided by the water within the alkaline solutionso that the application of water and alkaline can be carried out in asingle step. In this case, the concentration of the alkaline solutioncan be adjusted to provide the desired amount of water to alkalisedtobacco material. Alternatively, additional water may be added to thealkalised tobacco material, separately to the alkaline solution.

In methods according to the second aspect of the present invention, inwhich the alkaline treatment is carried out on the residual tobaccomaterial from the first heating step, the residual tobacco material willtypically have a low water content following the heating of the tobaccomaterial during the first heating step. In such methods, it will beparticularly important to restore the water content of the residualtobacco material to a level of between 10 percent and 20 percent byweight prior to the second heating step. As described above, thisremoistening of the residual tobacco material is preferably achievedthrough the inclusion of a sufficient amount of water in the alkalinesolution applied to the residual tobacco material.

As defined above, in the method of the present invention, the tobaccomaterial is heated under specific heating conditions to release thevolatile tobacco components, which are collected and formed into aliquid tobacco extract. In embodiments according to the first aspect ofthe invention in which the tobacco material is subjected to the alkalinetreatment prior to the heating step, the alkalised tobacco material willbe heated as described below.

During the heating step, the tobacco material is heated to an extractiontemperature of between about 100 degrees Celsius and about 160 degreesCelsius. It has been found that below this range, insufficient levels ofnicotine and certain flavour compounds are released from the tobaccomaterial such that the resultant liquid tobacco extract lacks thedesired flavour characteristics. On the other hand, if the tobaccomaterial is heated to a temperature above this defined range,unacceptably high levels of certain undesirable tobacco compounds may bereleased.

Preferably, the extraction temperature is at least about 110 degreesCelsius, more preferably at least about 115 degrees Celsius, morepreferably at least about 120 degrees Celsius, more preferably at leastabout 125 degrees Celsius.

Preferably, the extraction temperature is no more than about 150 degreesCelsius, more preferably no more than about 145 degrees Celsius, morepreferably no more than about 140 degrees Celsius, most preferably nomore than about 135 degrees Celsius.

For example, the extraction temperature may be between about 110 degreesCelsius and 150 degrees Celsius, or between about 120 degrees Celsiusand about 140 degrees Celsius, or between about 125 degrees Celsius andabout 135 degrees Celsius, or about 130 degrees Celsius. An extractiontemperature of around 130 degrees Celsius has been found to provide aparticularly optimised ratio of desirable to undesirable compounds inthe liquid tobacco extract.

The tobacco material is heated at the extraction temperature for atleast about 30 minutes, more preferably for at least about 40 minutes,more preferably for at least about 50 minutes, more preferably for atleast about 60 minutes. This extraction time is sufficiently long thatthe desired tobacco flavour compounds can be extracted efficiently toprovide a liquid tobacco extract that can produce an aerosol having thedesired flavour characteristics. The inclusion of the alkaline treatmentstep enables the heating step to be carried out relatively quickly, witha potentially shorter heating duration than is typically required inprior art extraction processes.

Preferably, the tobacco material is heated at the extraction temperaturefor no more than about 180 minutes, more preferably no more than about120 minutes.

For example, the tobacco material may be heated for between about 30minutes and about 180 minutes, or between about 30 minutes and about 120minutes, or between about 40 minutes and about 180 minutes, or betweenabout 40 minutes and about 120 minutes, or between about minutes andabout 180 minutes, or between about 50 minutes and about 120 minutes, orbetween about 60 minutes and about 180 minutes, or between about 60minutes and about 120 minutes

The heating time indicated above corresponds to the duration of timeover which the tobacco material is heated at the extraction temperatureand does not include the time taken to increase the temperature of thetobacco material up to the extraction temperature.

In methods according to the first aspect of the present invention inwhich the tobacco material is subjected to the alkaline treatment stepprior to the first heating step, the amount of nicotine extracted fromthe alkalised tobacco material during the heating step preferablycorresponds to at least about 10 grams per kg of dry tobacco material,more preferably at least about 12 grams per kg of dry tobacco material.As demonstrated in the example below, this extraction yield of nicotineis significantly higher than is possible using an equivalent extractionmethod but without the alkaline treatment step prior to heating.

Methods according to the second aspect of the present invention in whichthe residual tobacco material is subjected to an alkaline treatment stepinclude a second heating step to remove further volatile compounds, inparticular nicotine, from the residual tobacco material.

In such methods, during the first heating step, the tobacco material isheated to an extraction temperature of between about 100 degrees Celsiusand about 160 degrees Celsius. Preferably, the extraction temperature ofthe first extraction step is at least about 110 degrees Celsius, morepreferably at least about 115 degrees Celsius, more preferably at leastabout 120 degrees Celsius, more preferably at least about 125 degreesCelsius.

Preferably, the extraction temperature of the first extraction step isno more than about 150 degrees Celsius, more preferably no more thanabout 145 degrees Celsius, more preferably no more than about 140degrees Celsius, most preferably no more than about 135 degrees Celsius.

For example, the extraction temperature of the first extraction step maybe between about 110 degrees Celsius and 150 degrees Celsius, or betweenabout 120 degrees Celsius and about 140 degrees Celsius, or betweenabout 125 degrees Celsius and about 135 degrees Celsius, or about 130degrees Celsius. An extraction temperature of around 130 degrees Celsiushas been found to provide a particularly optimised ratio of desirable toundesirable compounds in the liquid tobacco extract.

During the first heating step, the tobacco material is heated at theextraction temperature for at least about 90 minutes, more preferablyfor at least about 120 minutes. Preferably, the tobacco startingmaterial is heated at the extraction temperature for no more than about270 minutes, more preferably no more than about 180 minutes. Forexample, the tobacco material may be heated for between about 90 minutesand about 270 minutes, or between about 90 minutes and about 180minutes, or between about 120 minutes and about 270 minutes, or betweenabout 120 minutes and about 180 minutes.

In the second heating step, the alkalised tobacco material is heated toan extraction temperature of between about 100 degrees and about 160degrees. The temperature of the second heating step may be the same asthe temperature selected for the first heating step, or it may bedifferent.

Preferably, the extraction temperature for the second heating step is atleast about 110 degrees Celsius, more preferably at least about 115degrees Celsius, more preferably at least about 120 degrees Celsius,more preferably at least about 125 degrees Celsius.

Preferably, the extraction temperature for the second heating step is nomore than about 150 degrees Celsius, more preferably no more than about145 degrees Celsius, more preferably no more than about 140 degreesCelsius, most preferably no more than about 135 degrees Celsius.

For example, the extraction temperature for the second heating step maybe between about 110 degrees Celsius and 150 degrees Celsius, or betweenabout 120 degrees Celsius and about 140 degrees Celsius, or betweenabout 125 degrees Celsius and about 135 degrees Celsius, or about 130degrees Celsius.

In such methods comprising a second heating step, the alkalised tobaccomaterial is preferably heated in the second heating step for at least 15minutes, more preferably at least 20 minutes, more preferably at least30 minutes, more preferably at least 40 minutes. The second heating stepwill typically be shorter than the first heating step. Preferably,during the second heating step, the alkalised tobacco material is heatedfor no more than about 120 minutes, more preferably no more than about90 minutes. For example, the alkalised tobacco material may be heatedfor between about 15 minutes and about 120 minutes, or between about 15minutes and about 90 minutes, or between about 20 minutes and about 120minutes, or between about 20 minutes and about 90 minutes, or betweenabout 30 minutes and about 120 minutes, or between about 30 minutes andabout 90 minutes, or between about 40 minutes and about 120 minutes, orbetween about 40 minutes and about 90 minutes.

Preferably, the extraction temperature and the extraction time for thesecond heating step are selected in order to maximise the extraction ofnicotine from the alkalised tobacco material.

The second heating step may be carried out in the same extractionchamber as the first heating step, or in a second extraction chamber.Where two extraction chambers are used for the separate heating steps,the extraction chambers may optionally be connected in order to achievea continuous flow of the tobacco material through the extractionapparatus.

In methods according to the second aspect of the present invention inwhich the alkaline treatment step is carried out on the residual tobaccomaterial after the first heating step, the additional amount of nicotineextracted from the alkalised tobacco material during the second heatingstep corresponds to at least about 1 gram per kg of dry tobaccomaterial, more preferably at least about 2 grams per kg of dry tobaccomaterial. This nicotine yield is in addition to the nicotine extractedfrom the tobacco material during the first heating step.

For each of the heating steps, the extraction temperature and theduration of heating may be selected within the ranges defined abovedepending upon factors such as the type of tobacco, possible othercomponents of the tobacco material, the desired level of nicotine or thedesired composition of the liquid tobacco extract. By controlling thecombination of extraction temperature and time, the composition of theliquid tobacco extract can be adjusted depending on the desiredcharacteristics of the aerosol generated from the liquid tobaccoextract. In particular, the proportion of specific tobacco compoundswithin the liquid tobacco extract can be adjusted to a certain degreethrough the selection of the extraction parameters in order to maximisethe ratio of desirable to undesirable tobacco compounds within theliquid tobacco extract.

For a specific tobacco compound, the variation in the level of releaseof the compound with extraction temperature during the extractionprocess can be readily determined for any given tobacco material. Forexample, it has been found that the level of nicotine released from atobacco material will typically increase with increasing extractiontemperature. The rate of increase has been found to vary for differenttobacco types.

It has also been found that the level of desirable tobacco flavourcompounds, such as β-damascenone and β-ionone, released from a tobaccomaterial will increase with increasing extraction temperature up to acertain peak extraction temperature, after which the level will begin todecrease. The peak extraction temperature for such flavour compounds istypically within the range of 120 degrees Celsius to 160 degrees Celsiussuch that the level of desirable flavour compounds can be effectivelyoptimised in the extraction method of the present invention.

Many undesirable tobacco compounds have been found to increase slowlywith increasing extraction temperature up to a threshold temperature,beyond which a rapid increase is observed. This applies, for example, tothe level of phenolic compounds, TSNAs and certain pyrazines and in thecase of Bright tobaccos, to the level of furans and formaldehyde. Inmany cases, the threshold temperature is within the range of 120 degreesCelsius to 160 degrees Celsius and therefore the level of theundesirable compounds can be effectively controlled in the extractionmethod of the present invention.

Preferably, the extraction temperature and extraction time are selectedto provide a nicotine content in the liquid tobacco extract of at least0.1 percent by weight, more preferably at least about 0.2 percent byweight.

Preferably, in methods according to the second aspect of the invention,the extraction temperature or the extraction time or both the extractiontemperature and the extraction time of the heating steps are selected toprovide a ratio by weight of (β-ionone+β-damascenone) to (phenol) of atleast about 0.25 in the liquid tobacco extract.

β-damascenone and β-ionone are desirable compounds associated withtobacco flavour. It has been found that the amount of 3-damascenone andβ-ionone released from a tobacco material will increase with increasingthe extraction temperature up to a certain peak extraction temperature,after which the level will begin to decrease. The peak extractiontemperature for such flavour compounds is typically within the range of120 degrees Celsius to 160 degrees Celsius such that the level ofdesirable flavour compounds can be effectively tailored and controlledin the extraction method.

Preferably, in methods according to the second aspect of the invention,the extraction temperature or the extraction time or both the extractiontemperature and the extraction time of the heating steps are selected toprovide a ratio by weight of(furaneol+(2,3-diethyl-5-methylpyrazine)*100)) to (nicotine) of at leastabout 5×10⁻⁴ in the liquid tobacco extract.

It has been found that in methods in accordance with the presentinvention wherein the extraction temperature is selected to provideratios within the ranges described above, particularly good sensoryprofiles may be attained when nicotine compositions prepared from liquidtobacco extracts are heated to generate an aerosol.

Suitable heating methods for carrying out the heating of the tobaccomaterial would be known to the skilled person and include but are notlimited to: dry distillation, hydrodistillation, vacuum distillation,flash distillation and thin film hydrodistillation.

The one or more heating steps are preferably carried out in an inertatmosphere. Preferably, a flow of an inert gas, such as nitrogen, ispassed through the tobacco material during the heating step. In somecases, a flow of a combination of an inert gas with water or steam maybe used. The addition of water or steam to the tobacco during extractionhas been found to increase yield of extracted components. However,excess addition of water or steam leads to processing difficulties suchas stickiness of the tobacco material.

The volatile tobacco compounds are released into the flow of inert gasduring the heating step such that the inert gas (or combination of inertgas with water or steam) acts as a carrier for the volatile components.The inert gas flow rate may be optimised based on the scale and geometryof the extraction chamber. A relatively high flow rate of inert gas mayadvantageously improve the efficiency of extraction from the tobaccomaterial.

In general, upon heating the tobacco material, any moisture present inthe tobacco material is also released with the volatile compounds, inthe form of steam.

The flow of inert gas helps convey the steam generated by evaporation ofthe moisture content of the tobacco material and the volatilecompounds—including, in particular, nicotine or flavour-associatedcompounds or both—out of the extraction equipment.

Further, use of a flow of inert gas, such as nitrogen, under lightover-pressure in the extraction equipment has the benefit of preventingthe presence of oxygen within the extraction equipment. This isdesirable in that it prevents risk of any, even partial, combustion ofthe tobacco material during the heating step. Uncontrolled combustion ofthe tobacco material would clearly be undesirable as it would representa major safety risk within the manufacturing environment. However, theinventors have found that even a limited, partial combustion of thetobacco material may lead to a decrease in the quality of the tobaccoextract obtainable by the method, which would be undesirable.

Without wishing to be bound by theory, it is understood that, bypreventing combustion of the tobacco material, the formation of anyundesirable combustion by-products is also prevented. Further, asconditions that would be conducive to combustion of the tobacco materialare prevented, the tobacco material is effectively heated underconditions that mimic, to an extent, conditions under which atobacco-containing substrate (e.g. homogenised tobacco material) istypically heated in “heat-not-burn” articles. As a result, selectiveextraction of the flavour-bearing volatile species responsible for thetaste consumers associate with heated tobacco is advantageouslyfavoured.

Therefore, by carrying out the heating step in an inert atmosphere, theextraction efficiency, product quality and manufacturing safety areadvantageously enhanced.

The heating of the tobacco material in a flow of inert gas has theadditional benefit that the inert gas flow containing the volatilecompounds may be more easily directed into a container containing anextraction solvent, such as a non-aqueous extraction liquid solvent.

Optionally, the heating step may be carried out under vacuum. Thisremoves any oxygen present within the extraction chamber, which mayadvantageously prevent reaction of the tobacco material or volatilecompounds generated upon heating of the tobacco material with oxygen.The removal of oxygen will also prevent any combustion of the tobaccomaterial, as described above.

Methods according to the present invention may further comprise the stepof spraying atomised water into the extraction chamber during theheating step. This has been found to improve heat exchange during theheating step, which is thought to be due to the turbulent flow that isset up within the extraction chamber as a result of the evaporation ofthe atomised water. As a result of the improved heat exchange, theinclusion of the step of spraying water into the extraction chamberduring the heating step has been found to provide a further improvementin the nicotine yield, as well as an increase in the yield of certaindesirable flavour compounds from the tobacco material.

The spray of atomised water may be generated and dispensed into theextraction chamber using any suitable means.

The flow rate at which the atomised water is sprayed into the extractionchamber may be adjusted, for example, depending upon the flow rate ofthe tobacco material within the extraction chamber. For example, theaverage flow rate at which the atomised water is sprayed into theextraction chamber may be between about 3 percent and about 30 percentof the flow rate of the tobacco material.

Preferably, the atomised water is sprayed at a pressure of at leastabout 1 bar, more preferably at least about 2 bar, more preferably atleast about 3 bar.

Methods of atomising water would be known to the skilled person. In someembodiments, the water may be atomised in a flow of compressed inertgas, such as air. In other embodiments, the water may be atomisedwithout a flow of gas, due to the pressure within the spray nozzle.

The liquid tobacco extract may be produced from a tobacco materialconsisting of a single type of natural tobacco. Alternatively, thetobacco material may comprise a blend of two or more types of naturaltobaccos. The ratio of the different tobacco types may be adapteddepending on the desired characteristics of the aerosol generated fromthe liquid tobacco extract. For example, where it is desired to providea relatively high level of nicotine, the proportion of Burley tobaccomay be increased.

The term “natural tobacco” is used herein with reference to the presentinvention to describe any part of any plant member of the genusNicotiana, including, but not limited to, leaves, midribs, stems andstalks. In particular, the natural tobacco may comprise flue-curedtobacco material, Burley tobacco material, Oriental tobacco material,Maryland tobacco material, dark tobacco material, dark-fired tobaccomaterial, Rustica tobacco material, as well as material from other rareor specialty tobaccos, or blends thereof. As will be described in moredetail below, the tobacco material may be whole (for example, wholetobacco leaves), shredded, cut or ground.

Where it is desired to produce a liquid tobacco extract from acombination of two of more different tobacco types, the tobacco typesmay be heated separately at different extraction temperatures within thedefined range of 100 degrees Celsius to 160 degrees Celsius, or amixture of the tobacco types may be heated together at a singleextraction temperature within the range.

The tobacco material may be a solid tobacco material, such as a powder,leaf scraps or shreds, or intact leaf. Alternatively, the tobaccomaterial may be a liquid tobacco material such as a dough, gel, slurry,or suspension.

The tobacco material may be derived from any suitable tobacco material,including but not limited to tobacco leaf, tobacco stem, reconstitutedtobacco, cast tobacco, extruded tobacco or tobacco derived pellets.

Preferably, in the step of preparing the tobacco material, the tobaccois ground or cut in order to reduce the size of tobacco particles withinthe tobacco material. This may advantageously improve the homogeneity ofheating of the tobacco material and the efficiency of the extraction.

The tobacco material may optionally be dried prior to the heating stepin order to decrease the water content of the tobacco material. Dryingof the tobacco material may be carried out by any suitable chemical orphysical drying process. Alternatively, water may be added to thetobacco material prior to the heating step in order to increase thewater content of the tobacco material.

In certain embodiments of the present invention, the step of preparingthe tobacco material may comprise the step of impregnating the tobaccomaterial with an aerosol former. When this impregnation of the tobaccomaterial is carried out prior to the heating step, it may advantageouslyincrease the amount of certain desirable tobacco compounds that arereleased from the tobacco material upon heating. For example,impregnation of the tobacco material with glycerin has been found toadvantageously increase the amount of nicotine that is extracted fromthe tobacco material. In another example, impregnation of the tobaccomaterial with a non-aqueous extraction solvent that is also an aerosolformer, such as propylene glycol, vegetal glycerin, 1,3-propanediol,triacetin, or mixtures thereof has been found to advantageously increasethe amount of flavour compounds that are extracted from the tobaccomaterial.

In some embodiments, the tobacco material consists of natural tobaccothat has not been subjected to any pre-treatment steps, for example, toadjust the water content. As such, a water content in the tobaccomaterial may be about 10 to 20 percent by weight (water contenttypically found in natural tobacco material). In other embodiments, thetobacco material may comprise added water, as described above.

Alternatively or in addition, the tobacco material may comprise one ormore additional ingredients, such as for example a non-aqueous solvent.An example of a suitable solvent is propylene glycol.

The tobacco material may thus comprise at least about 40 percent byweight of natural tobacco material or at least about 60 percent byweight of natural tobacco material or at least about 80 percent byweight of natural tobacco material or at least about 90 percent byweight of natural tobacco material or at least about 95 percent byweight of natural tobacco material.

The water content in the tobacco starting material may be at least about3 percent by weight. Preferably, the water content in the tobaccostarting material is at least about 5 percent by weight. Morepreferably, the water content in the tobacco starting material is atleast about 5 percent by weight. It will be appreciated that “the watercontent in the tobacco starting material” may include both waterinherently present in the natural tobacco material as well as any addedwater.

The water content in the tobacco starting material may be less than orequal to about 60 percent by weight. Preferably, the water content inthe tobacco starting material is less than or equal to about 20 percentby weight. More preferably, the water content in the tobacco startingmaterial is less than or equal to about 12 percent by weight.

In some embodiments, the water content in the tobacco starting materialmay be from about 3 percent by weight to about 60 percent by weight,more preferably from about 3 percent by weight to about 20 percent byweight, even more preferably from about 3 percent by weight to about 12percent by weight. In other embodiments, the water content in thetobacco starting material may be from about 5 percent by weight to about60 percent by weight, more preferably from about 5 percent by weight toabout 20 percent by weight, even more preferably from about 5 percent byweight to about 12 percent by weight. In further embodiments, the watercontent in the tobacco starting material may be from about 8 percent byweight to about 60 percent by weight, more preferably from about 8percent by weight to about 20 percent by weight, even more preferablyfrom about 8 percent by weight to about 12 percent by weight.

In some embodiments, the non-aqueous solvent content may be at leastabout 5 percent by weight or at least about 10 percent by weight or atleast about 15 percent by weight or at least about 20 percent by weightor at least about 25 percent by weight or at least about 30 percent byweight or at least about 35 percent by weight or at least about 40percent by weight.

Optionally, the tobacco material may be digested enzymatically prior tothe heating step. This has been found to provide a significant increasein the yield of certain flavour compounds from the tobacco material.

The tobacco material may optionally be analysed prior to the heatingstep in order to determine the composition, for example, the content ofreducing sugars of alkaloids. This information about the composition mayhelpfully be used to select an appropriate extraction temperature.

Methods according to the invention may further comprise the step ofmicrowave heating the tobacco material during at least one step of themethod. The tobacco material may be microwave heated during apre-treatment step, prior to the heating step. Alternatively or inaddition, the tobacco material may be microwave heated during the mainheating step, either instead of conventional heating or in combinationwith conventional heating.

The inclusion of a microwave heating step in the extraction method ofthe present invention has been found to provide a further improvement inthe extraction yield of nicotine.

During the heating of the tobacco material, the volatile compounds arereleased in gaseous form from the tobacco material. The volatilecompounds are collected using any suitable technique. Where the tobaccomaterial is heated in a flow of an inert gas, as described above, thevolatile compounds are collected from the inert gas flow. Differentcollection methods would be well known to the skilled person.

In certain preferred embodiments, the step of collecting the volatilecompounds uses an absorption technique in which the volatile compoundsare trapped in a non-aqueous extraction liquid solvent. For example, aninert gas flow containing the volatile compounds may be directed into acontainer of a non-aqueous extraction liquid solvent. The non-aqueousextraction liquid solvent is preferably an aerosol former such astriacetin, glycerin, 1,3-propanediol, propylene glycol or combinationsthereof. The use of an aerosol former as the liquid solvent ispotentially beneficial because the aerosol former can be retained as adiluting agent in the final liquid tobacco extract. This means that anadditional step of removing the non-aqueous extraction solvent is notnecessarily required.

As used herein with reference to the present invention, the term“aerosol former” refers to a compound or mixture of compounds that, inuse, facilitates formation of an aerosol, and that preferably issubstantially resistant to thermal degradation at the operatingtemperature of the aerosol-generating article or device. Examples ofsuitable aerosol-formers include: polyhydric alcohols, such as propyleneglycol, triethylene glycol, 1,3-propanediol, and glycerin; esters ofpolyhydric alcohols, such as glycerol mono-, di- or triacetate; andaliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyldodecanedioate and dimethyl tetradecanedioate.

Preferably, the non-aqueous liquid solvent is retained at a temperatureof less than 0 degrees Celsius in order to optimise the transfer of thevolatile compounds into the liquid solvent. The non-aqueous extractionsolvent is preferably retained at a temperature of no less than −10degrees Celsius. Temperatures below such value may lead to undesirablefreezing phenomena.

In alternative preferred embodiments, the step of collecting thevolatile compounds may be carried out using a condensation technique inwhich the volatile compounds are condensed and the condensate ofvolatile compounds is collected. Condensation of the volatile compoundsmay be carried out using any suitable apparatus, for example, in arefrigerated column. Preferably, the condensate obtained is added to aliquid aerosol former, preferably propylene glycol.

The addition of a liquid aerosol former in the collection step, andparticularly addition of propylene glycol, may advantageously preventthe condensed volatile compounds from splitting into two phases orforming an emulsion, as some tobacco constituents would tend to do.Without wishing to be bound by theory, the inventors have observed thatthe solubility of the tobacco constituents in the hydrolate (i.e. theaqueous fraction of the liquid, naturally derived tobacco extract)depends primarily on their polarity, on their concentration and on thepH of the hydrolate, which may vary depending on the tobacco type. As aresult, an oily layer tends to form at the surface of the liquid,naturally derived tobacco extract, if the amount of aerosol former isnot sufficient. Such oily material can aggregate at different locationson the trapping and desiccation equipment wherein the third and furthersteps of the method are carried out, respectively. The addition of aliquid aerosol former, such as propylene glycol, helps prevent theformation of such layer and favours homogenisation of the liquid,naturally derived tobacco extract. This, in turn, helps prevent any lossof desirable flavour-associated compounds during the fourth(desiccation) step, during which such compounds may undesirably depositon the equipment surfaces.

In addition, the liquid aerosol former advantageously helps trap theflavour-associated compounds independent of their polarity andvolatility. Further, during any subsequent drying step, the liquidaerosol former helps prevent loss of the most volatile fraction, as wellas favour the selective removal of excess water from the liquid,naturally derived tobacco extract to obtain the concentrated tobaccoextract.

Use of propylene glycol as the aerosol former for the collection stephas the further advantage that, by reducing the water activity ofaqueous solutions, propylene glycol exerts an anti-microbial activity.By adjusting the content of propylene glycol in the liquid tobaccoextract, it is therefore also possible to ensure that the extractsubstantially does not undergo any microbial activity.

As a further alternative, the step of collecting the volatile compoundsmay be carried out using an adsorption technique in which the volatilecompounds are adsorbed onto the surface of a solid adsorbent material,such as activated carbon. The adsorbed compounds are then transferredinto a liquid solvent.

In the method of the present invention, the next step is the formationof a liquid tobacco extract from the collected volatile compounds. Thenature of this step may depend upon the collection method. The“collected volatile compounds” will typically comprise a solution of thetobacco derived volatile compounds in a liquid solvent or carrier.

Where the volatile compounds are collected by absorption in anon-aqueous extraction solvent, as described above, the extractionmethod provides a liquid tobacco extract that may comprise greater thanabout 25 percent by weight of the non-aqueous extraction solvent basedon the weight of the liquid tobacco extract. In some embodiments, theliquid tobacco extract may comprise greater than about 30 percent byweight of the non-aqueous extraction solvent based on the weight of theliquid tobacco extract or greater than about 35 percent by weight ofnon-aqueous extraction solvent based on the weight of the liquid tobaccoextract.

The liquid tobacco extract may comprise less than or equal to about 65percent of non-aqueous extraction solvent based on the weight of theliquid tobacco extract. In some embodiments, the liquid tobacco extractmay comprise less than or equal to 60 percent of non-aqueous extractionsolvent based on the weight of the liquid tobacco extract or less thanor equal to 55 percent of non-aqueous extraction solvent based on theweight of the liquid tobacco extract.

In some embodiments, the liquid tobacco extract may comprise from about25 percent by weight of the non-aqueous extraction solvent based on theweight of the liquid tobacco extract to about 65 percent by weight ofthe non-aqueous extraction solvent based on the weight of the liquidtobacco extract. The liquid tobacco extract may comprise from about 25percent by weight of the non-aqueous extraction solvent based on theweight of the liquid tobacco extract to about 60 percent by weight ofthe non-aqueous extraction solvent based on the weight of the liquidtobacco extract. The liquid tobacco extract may comprise from about 25percent by weight of the non-aqueous extraction solvent based on theweight of the liquid tobacco extract to about 55 percent by weight ofthe non-aqueous extraction solvent based on the weight of the liquidtobacco extract.

In other embodiments, the liquid tobacco extract may comprise from about30 percent by weight of the non-aqueous extraction solvent based on theweight of the liquid tobacco extract to about 65 percent by weight ofthe non-aqueous extraction solvent based on the weight of the liquidtobacco extract. The liquid tobacco extract may comprise from about 30percent by weight of the non-aqueous extraction solvent based on theweight of the liquid tobacco extract to about 60 percent by weight ofthe non-aqueous extraction solvent based on the weight of the liquidtobacco extract. The liquid tobacco extract may comprise from about 30percent by weight of the non-aqueous extraction solvent based on theweight of the liquid tobacco extract to about 55 percent by weight ofthe non-aqueous extraction solvent based on the weight of the liquidtobacco extract.

In further embodiments, the liquid tobacco extract may comprise fromabout 35 percent by weight of the non-aqueous extraction solvent basedon the weight of the liquid tobacco extract to about 65 percent byweight of the non-aqueous extraction solvent based on the weight of theliquid tobacco extract. The liquid tobacco extract may comprise fromabout 35 percent by weight of the non-aqueous extraction solvent basedon the weight of the liquid tobacco extract to about percent by weightof the non-aqueous extraction solvent based on the weight of the liquidtobacco extract. The liquid tobacco extract may comprise from about 35percent by weight of the non-aqueous extraction solvent based on theweight of the liquid tobacco extract to about 55 percent by weight ofthe non-aqueous extraction solvent based on the weight of the liquidtobacco extract. The non-aqueous extraction solvent is preferablytriacetin, glycerin, propylene glycol, 1,3-propanediol or a mixturethereof.

In preferred embodiments, in the liquid tobacco extract a ratio byweight of (6-ionone+6-damascenone) to (phenol) is at least about 0.25.

In preferred embodiments, in the liquid tobacco extract a ratio byweight of (furaneol+(2,3-diethyl-5-methylpyrazine)*100)) to (nicotine)is at least about 5×10⁻⁴.

Where the volatile compounds are collected by absorption in a liquidsolvent, as described above, the step of forming the liquid tobaccoextract preferably comprises drying the solution of the volatilecompounds in the liquid solvent in order to concentrate the solution.This may be carried out, for example, in order to arrive at a desiredconcentration of nicotine, or flavour compounds. Drying may be carriedout using any suitable means, including but not limited to desiccation,molecular sieves, freeze drying, phase separation, distillation,membrane permeation, controlled crystallisation of water and filtering,reverse hygroscopicity, ultracentrifugation, liquid chromatography,reverse osmosis or chemical drying.

In preferred embodiments, the solution of the volatile compounds in aliquid solvent is concentrated by desiccation.

In other words, the solution of the volatile compounds in a liquidsolvent is heated to evaporate at least some of the water and obtain aconcentrated tobacco extract. To this purpose, the solution of thevolatile compounds in a liquid solvent may be heated to a temperatureand for a time such that the water content in the tobacco extract isreduced by at least about 60 percent.

The partially desiccated, concentrated tobacco extract can be consideredthe primary product of a method in accordance with the presentinvention. Depleted tobacco material, from which the volatile speciesand most of the moisture content have been extracted upon heating duringthe second step, may be considered a by-product of the method. Suchdepleted tobacco material may typically have a moisture content of about1 to 5 percent by weight, preferably about 2 to 3 percent by weight.

In an embodiment, the solution of the volatile compounds in a liquidsolvent is heated under vacuum, preferably at a temperature of at leastabout 70 degrees Celsius. In another embodiment, the solution of thevolatile compounds in a liquid solvent is heated under a flow of air,preferably under a flow of air having relatively low humidity, at atemperature of at least about degrees Celsius. Thus, a naturallyderived, concentrated tobacco extract can be obtained by a method inaccordance with the invention. One such naturally derived, concentratedtobacco extract typically contains less than about 20 percent by weightof water.

Alternatively, where the volatile compounds are collected bycondensation, the step of forming the liquid tobacco extract maycomprise adding the condensate to a liquid solvent, such as an aerosolformer.

Optionally, the step of forming the liquid tobacco extract comprises afiltering step.

Optionally, the step of forming the liquid tobacco extract comprises ablending step in which extracts derived from different tobacco materialsare combined.

Optionally, the step of forming the liquid tobacco extract comprisesadding one or more additives, such as an organic acid, to the solutionof volatile compounds. However, in many cases the liquid tobacco extractis suitable for use without the inclusion of additives.

In embodiments according to the second aspect of the present inventionin which the alkaline treatment step is carried out on the residualtobacco material from the first heating step, two separate liquidtobacco extracts are produced during the extraction method: a firstliquid tobacco extract from the first heating step of the tobaccomaterial and a second liquid tobacco extract from the second heatingstep of the alkalised tobacco material. Preferably, such methods furthercomprise the step of combining the first liquid tobacco extract and thesecond liquid tobacco extract.

In certain embodiments, the nicotine from the second liquid tobaccoextract may be isolated and at least a portion of the isolated nicotinemay be added to the first liquid tobacco extract. This produces a liquidtobacco extract with an enhanced level of nicotine, without impactingthe flavour characteristics of the first liquid tobacco extract.

The present invention further provides a liquid tobacco extract producedby a method according to the invention, as described in detail above. Asdescribed above, the method of the present invention advantageouslyproduces a natural liquid tobacco extract that has a highly desirableratio of desired tobacco compounds, such as nicotine and flavourcompounds, to undesirable tobacco compounds.

The liquid tobacco extract is particularly suitable for producing anicotine composition, such as a liquid nicotine composition or a gelnicotine composition, for use in an aerosol-generating system. In suchan aerosol-generating system, the nicotine composition is typicallyheated within an aerosol-generating device.

As used herein, the term “aerosol generating device” refers to a devicecomprising a heater element that interacts with a nicotine compositionincorporating a liquid tobacco extract such as that obtained by a methodin accordance with the invention to produce an aerosol. During use,volatile compounds are released from the nicotine composition by heattransfer and entrained in air drawn through the aerosol generatingdevice. As the released compounds cool they condense to form an aerosolthat is inhaled by the consumer.

Upon heating of a nicotine composition comprising the liquid tobaccoextract according to the present invention, an aerosol is releasedcontaining the volatile compounds that have been collected from thetobacco material during the extraction process. By controlling thecomposition of the liquid tobacco extract through control of theparameters of the extraction parameter, it is possible to adjust thecomposition and characteristics of the resultant aerosol produced fromthe liquid tobacco extract and delivered to the consumer.

The nicotine composition may be a liquid tobacco extract resulting froman extraction process in accordance with the present invention, withoutthe addition of further nicotine. The nicotine composition may be aliquid tobacco extract resulting from an extraction process inaccordance with the present invention, without the addition of furtherflavour compounds. The nicotine composition may be a liquid tobaccoextract resulting from an extraction process in accordance with thepresent invention, without the addition of further furaneol. Thenicotine composition may be a liquid tobacco extract resulting from anextraction process in accordance with the present invention, without theaddition of further solvent.

Alternatively, the liquid tobacco extract may be subjected to additionalprocessing steps to form the nicotine composition. Even when subjectedto such additional steps, the nicotine composition may be formed withoutthe need for addition of further nicotine or flavour compounds.

Preferably, the liquid tobacco extract may be concentrated in adesiccation step as described above to form a concentrated tobaccoextract, and the concentrated tobacco extract may be used to form thenicotine composition.

Preferably, the concentrated tobacco extract comprises between 8 percentand 15 percent by weight water based on the weight of the concentratedtobacco extract.

The desiccation step provides a concentrated tobacco extract that mayhave a non-aqueous extraction solvent content of from about 65 percentto about 95 percent by weight, preferably from about 65 percent to 85percent by weight, most preferably from about 75 percent to about 85percent by weight. The non-aqueous extraction solvent is preferablytriacetin, glycerin, propylene glycol, 1,3-propanediol or a mixturethereof.

The desiccation step provides a concentrated tobacco extract that mayhave a nicotine content of at least about 0.2 percent by weightnicotine, preferably from about 0.5 percent by weight to about 12percent by weight nicotine, most preferably from about 2 percent byweight to about 8 percent by weight nicotine.

Preferably, additional non-aqueous solvent may be added to the liquidtobacco extract or the concentrated tobacco extract to form the nicotinecomposition.

The nicotine composition may be a liquid nicotine composition or a gelnicotine composition.

The nicotine composition may comprise at least about 10 percent byweight of a liquid tobacco extract. Preferably, the nicotine compositioncomprises at least about 20 percent by weight of a liquid tobaccoextract. More preferably, the nicotine composition comprises at leastabout 30 percent by weight of a liquid tobacco extract. In preferredembodiments, the nicotine composition comprises at least about 40percent by weight of a liquid tobacco extract, more preferably at leastabout 50 percent by weight of a liquid tobacco extract, even morepreferably at least about 60 percent by weight of a liquid tobaccoextract. In particularly preferred embodiments, the nicotine compositioncomprises at least about 65 percent by weight of a liquid tobaccoextract, more preferably at least about 70 percent by weight of a liquidtobacco extract, even more preferably at least about 75 percent byweight of a liquid tobacco extract, most preferably at least about 80percent by weight of a liquid tobacco extract.

In some embodiments, the liquid tobacco extract is concentrated tobaccoextract. The nicotine composition may comprise at least about 10 percentby weight of concentrated tobacco extract, at least about 20 percent byweight of concentrated tobacco extract, at least about 30 percent byweight of concentrated tobacco extract, at least about 40 percent byweight of concentrated tobacco extract, at least about 50 percent byweight of concentrated tobacco extract, preferably at least about 60percent by weight of concentrated tobacco extract, more preferably atleast about 70 percent by weight of concentrated tobacco extract, evenmore preferably at least about 75 percent by weight of concentratedtobacco extract, and most preferably at least about 80 percent by weightof concentrated tobacco extract.

In some embodiments, the nicotine composition comprises from about 40percent by weight to about 95 percent by weight of a liquid tobaccoextract. More preferably, the nicotine composition comprises from about40 percent by weight to about 95 percent by weight of a liquid tobaccoextract. Even more preferably, the nicotine composition comprises fromabout 50 percent by weight to about 95 percent by weight of a liquidtobacco extract. Most preferably, the nicotine composition comprisesfrom about 60 percent by weight to about 95 percent by weight of aliquid tobacco extract. In some particularly preferred embodiments, thenicotine composition comprises from about 70 percent by weight to about95 percent by weight of a liquid tobacco extract, even more preferablyfrom about 80 percent by weight to about 95 percent by weight of aliquid tobacco extract.

In some embodiments, the nicotine composition comprises from about 40percent by weight to about 90 percent by weight of a liquid tobaccoextract. More preferably, the nicotine composition comprises from about40 percent by weight to about 90 percent by weight of a liquid tobaccoextract. Even more preferably, the nicotine composition comprises fromabout 50 percent by weight to about 90 percent by weight of a liquidtobacco extract. Most preferably, the nicotine composition comprisesfrom about 60 percent by weight to about 90 percent by weight of aliquid tobacco extract. In some particularly preferred embodiments, thenicotine composition comprises from about 70 percent by weight to about90 percent by weight of a liquid tobacco extract, even more preferablyfrom about 80 percent by weight to about 90 percent by weight of aliquid tobacco extract.

In some embodiments, the nicotine composition comprises from about 40percent by weight to about 85 percent by weight of a liquid tobaccoextract. More preferably, the nicotine composition comprises from about40 percent by weight to about 85 percent by weight of a liquid tobaccoextract. Even more preferably, the nicotine composition comprises fromabout 85 percent by weight to about 90 percent by weight of a liquidtobacco extract. Most preferably, the nicotine composition comprisesfrom about 60 percent by weight to about 85 percent by weight of aliquid tobacco extract. In some particularly preferred embodiments, thenicotine composition comprises from about 70 percent by weight to about85 percent by weight of a liquid tobacco extract, even more preferablyfrom about 80 percent by weight to about 85 percent by weight of aliquid tobacco extract.

The nicotine composition may comprise up to about 100 percent by weightof a liquid tobacco extract. In some embodiments, the nicotinecomposition may be formed directly from the liquid tobacco extractwithout the need for addition of additional non-aqueous solvent,flavourants or nicotine. That is to say, the nicotine composition maycomprise 100 percent by weight of a liquid tobacco extract. In someembodiments, the liquid tobacco extract is concentrated tobacco extract,such that the nicotine composition may comprise 100 percent by weight ofconcentrated tobacco extract. In embodiments in which the nicotinecomposition comprises 100 percent by weight of a liquid tobacco extractor 100 percent by weight of concentrated tobacco extract, additionalnon-aqueous solvent is not present.

Alternatively, in some embodiments, the nicotine composition comprisingliquid tobacco extract may comprise additional non-aqueous solvent.Additional non-aqueous solvent is non-aqueous solvent that has beenadded after the extraction step. Additional non-aqueous solvent issolvent that is supplemental to the non-aqueous extraction solventpresent in the liquid tobacco extract. In embodiments in which theliquid tobacco extract is concentrated tobacco extract, the nicotinecomposition comprising concentrated tobacco extract may compriseadditional non-aqueous solvent.

The additional non-aqueous solvent may be an aerosol former. Preferably,the additional non-aqueous solvent is triacetin, glycerin, propyleneglycol, 1,3-propanediol or a mixture thereof.

In embodiments in which the nicotine composition comprises additionalnon-aqueous solvent, the nicotine composition may comprise 90 percent byweight or less of the additional non-aqueous solvent. Preferably, thenicotine composition comprises 80 percent by weight or less of theadditional non-aqueous solvent. More preferably, the nicotinecomposition comprises 70 percent by weight or less of the additionalnon-aqueous solvent. In preferred embodiments, the nicotine compositioncomprises about 60 percent by weight or less of the additionalnon-aqueous solvent, more preferably about 50 percent by weight or lessof the additional non-aqueous solvent, even more preferably about 40percent by weight or less of the additional non-aqueous solvent. Inparticularly preferred embodiments, the nicotine composition comprisesabout 35 percent by weight or less of the additional non-aqueoussolvent, more preferably about 30 percent by weight or less of theadditional non-aqueous solvent, even more preferably about 25 percent byweight or less of the additional non-aqueous solvent, most preferablyabout 20 percent by weight or less of the liquid tobacco extract.

In a nicotine composition prepared by means of a method in accordancewith the present invention at least 50 percent by weight based on thetotal weight of the nicotine composition of the nicotine content in thenicotine composition may come from the tobacco extract as opposed tobeing added following extraction. In preferred embodiments, at least 80percent by weight based on the total weight of the nicotine compositionof the nicotine content in the nicotine composition comes from thetobacco extract as opposed to being added following extraction.

Even more preferably, at least 90 percent by weight based on the totalweight of the nicotine composition of the nicotine content in thenicotine composition comes from the tobacco extract as opposed to beingadded following extraction.

In a nicotine composition prepared by means of a method in accordancewith the present invention at least 50 percent by weight based on thetotal weight of the nicotine composition of the non-aqueous extractionsolvent content in the nicotine composition may come from the tobaccoextract as opposed to being added following extraction. In preferredembodiments, at least 80 percent by weight based on the total weight ofthe nicotine composition of the non-aqueous extraction solvent contentin the nicotine composition comes from the tobacco extract as opposed tobeing added following extraction. Even more preferably, at least 90percent by weight based on the total weight of the nicotine compositionof the non-aqueous extraction solvent content in the nicotinecomposition comes from the tobacco extract as opposed to being addedfollowing extraction.

In a nicotine composition prepared by means of a method in accordancewith the present invention at least 50 percent by weight based on thetotal weight of the nicotine composition of the water content in thenicotine composition may come from the tobacco extract as opposed tobeing added following extraction. In preferred embodiments, at least 80percent by weight based on the total weight of the nicotine compositionof the water content in the nicotine composition comes from the tobaccoextract as opposed to being added following extraction. Even morepreferably, at least 90 percent by weight based on the total weight ofthe nicotine composition of the water content in the nicotinecomposition comes from the tobacco extract as opposed to being addedfollowing extraction.

In a nicotine composition prepared by means of a method in accordancewith the present invention at least 50 percent by weight based on thetotal weight of the nicotine composition of the desirable tobaccoflavour species content in the nicotine composition may come from thetobacco extract as opposed to being added following extraction. Inpreferred embodiments, at least 80 percent by weight based on the totalweight of the nicotine composition of the desirable tobacco flavourspecies content in the nicotine composition comes from the tobaccoextract as opposed to being added following extraction. Even morepreferably, at least 90 percent by weight based on the total weight ofthe nicotine composition of the desirable tobacco flavour speciescontent in the nicotine composition comes from the tobacco extract asopposed to being added following extraction.

The total content of non-aqueous solvent in the nicotine compositionincludes the non-aqueous extraction solvent and the additionalnon-aqueous solvent, if it is present. The nicotine composition maycomprise a total content of non-aqueous solvent of from about 10 percentto about 95 percent by weight. The nicotine composition preferablycomprises a total content of non-aqueous solvent of from about 50percent to about 95 percent by weight, for example from about 65 percentto about 95 percent by weight, more preferably from about 70 to about 90percent by weight, most preferably from about 80 percent to about 90percent by weight. The non-aqueous solvent is preferably triacetin,glycerine, propylene glycol, 1,3-propanediol or a mixture thereof.

The nicotine composition may comprise a total content of propyleneglycol of from about 10 percent to about 95 percent by weight. Thenicotine composition may comprise a total content of propylene glycol offrom about 20 percent to about 95 percent by weight, such as from about50 percent to about 95 percent by weight, or from about 65 percent toabout 95 percent by weight, from about 70 to about 90 percent by weight,or from about 80 percent to about 90 percent by weight.

The nicotine composition may comprise a total content of triacetin offrom about 10 percent to about 95 percent by weight. The nicotinecomposition may comprise a total content of triacetin of from about 20percent to about 95 percent by weight, such as from about 50 percent toabout percent by weight, from about 70 to about 90 percent by weight orfrom about 65 percent to about 95 percent by weight, or from about 80percent to about 90 percent by weight.

The nicotine composition may comprise a total content of glycerine offrom about 10 percent to about 95 percent by weight. The nicotinecomposition may comprise a total content of glycerine of from about 20percent to about 95 percent by weight, such as from about 50 percent toabout percent by weight, or from about 65 percent to about 95 percent byweight, from about 70 to about 90 percent by weight or from about 80percent to about 90 percent by weight.

The nicotine composition may comprise a total content of 1,3-propanediolof from about 10 percent to about 95 percent by weight. The nicotinecomposition may comprise a total content of 1,3-propanediol of fromabout 20 percent to about 95 percent by weight, such as from about 50percent to about 95 percent by weight, or from about 65 percent to about95 percent by weight, or from about 80 percent to about 90 percent byweight.

The nicotine composition of the present invention comprises at least 0.2percent by weight of nicotine. More preferably, the nicotine content inthe nicotine composition liquid tobacco extract is at least about 0.4percent by weight. The nicotine composition may have a nicotine contentof about 12 percent by weight or less, for example about 10 percent byweight or less, preferably about 8 percent by weight by weight or less,more preferably about 5 percent by weight or less, preferably about 3.6percent by weight or less. Most preferably, the nicotine compositioncomprises between about 0.4 percent by weight and 3.6 percent by weightnicotine, based on the weight of the nicotine composition.

The nicotine composition may comprise between 1 percent and 85 percentby weight of water. The nicotine composition may comprise between 2percent and 50 percent by weight of water. The nicotine composition maycomprise between 3 percent and 30 percent by weight of water. Thenicotine composition may comprise between 5 percent and 25 percent byweight of water. The nicotine composition may comprise between 8 percentand 20 percent by weight of water. The nicotine composition preferablycomprises between 10 percent and 15 percent by weight water.

In some embodiments, the nicotine composition may comprise one or morewater-soluble organic acids. As used herein with reference to theinvention, the term “water-soluble organic acid” describes an organicacid having a water solubility at 20° C. of greater than or equal toabout 500 mg/ml.

The one or more water-soluble organic acids may advantageously bindnicotine in the liquid tobacco extract through formation of one ornicotine salts. The one or more nicotine salts may advantageously bedissolved and stabilised in the water present in the liquid tobaccoextract or in the non-aqueous solvent. This may advantageously reducenicotine adsorption in the upper airways and enhance pulmonary nicotinedelivery and retention as discussed above.

Preferably, the nicotine composition has a water-soluble organic acidcontent of greater than or equal to about 2 percent by weight. Morepreferably, the nicotine composition has a water-soluble organic acidcontent of greater than or equal to about 3 percent by weight.

The water-soluble organic acid may be acetic acid.

Exogenous acetic acid is acetic acid that has been added from a sourceother than the tobacco plant material, and is not acetic acid that isnaturally present in the tobacco plant that has been separated from,removed from or derived from the tobacco plant material using theextraction processing conditions and techniques.

If acetic acid is added to the liquid tobacco extract to form thenicotine composition, then the total content of acetic acid in thenicotine composition, including both exogenous and endogenous aceticacid, is preferably from about 0.01 percent to about 8 percent byweight, for example between about 0.03 percent to about 8 percent byweight, from about 0.3 percent to about 8 percent by weight, from about2 percent to about 8 percent by weight, or from about 3 percent to about8 percent by weight. More preferably, the total acetic acid content isfrom about percent to about 6 percent by weight, for example betweenabout 0.03 percent to about 6 percent by weight, from about 0.3 percentto about 6 percent by weight, from about from about 2 percent to about 6percent by weight, or from about 3 percent to about 6 percent by weight.

Preferably, the nicotine composition has a water-soluble organic acidcontent of less than or equal to about 8 percent by weight. Morepreferably, the nicotine composition has a water-soluble organic acidcontent of less than or equal to about 6 percent by weight.

Preferably, the nicotine composition has a water-soluble organic acidcontent of between about 2 percent by weight and about 8 percent byweight. For example, the nicotine composition may have a water-solubleorganic acid content of between about 2 percent by weight and about 6percent by weight.

More preferably, the nicotine composition has a water-soluble organicacid content of between about 3 percent by weight and about 8 percent byweight. For example, the nicotine composition may have a water-solubleorganic acid content of between about 3 percent by weight and about 6percent by weight.

The nicotine composition may comprise one or more non-tobacco-derivedflavourants. Suitable non-tobacco-derived flavourants include, but arenot limited to, menthol.

Preferably, the nicotine composition has a non-tobacco-derivedflavourant content of less than or equal to about 4 percent by weight.More preferably, the nicotine composition has a non-tobacco-derivedflavourant content of less than or equal to about 3 percent by weight.For example, the liquid tobacco extract produced by the method of thepresent invention may be used to make a nicotine composition comprisingbetween 10 and 20 mg of nicotine per millilitre, without the need foraddition of nicotine.

A nicotine composition suitable for use in an aerosol-generating systemmay comprise the liquid tobacco extract produced in a method accordingto the present invention in combination with water and additionalaerosol former. The nicotine composition may comprise, for example,between about 10 percent by weight and about 20 percent by weight ofwater.

A nicotine composition comprising the liquid tobacco extract accordingto the present invention may be provided in a cartridge for use in anaerosol-generating system. The cartridge may comprise an atomiser,configured to generate an aerosol from the nicotine composition. Theatomiser may be a thermal atomiser, which is configured to heat thenicotine composition to generate an aerosol. The thermal atomiser maycomprise, for example, a heater and a liquid transport elementconfigured to transport the nicotine composition to the heater. Theliquid transport element may comprise a capillary wick. Alternatively,the atomiser may be a non-thermal atomiser, which is configured togenerate an aerosol from the nicotine composition by means other thanheating. The non-thermal atomiser may be, for example, an impinging jetatomiser, an ultrasonic atomiser or a vibrating mesh atomiser.

The cartridge containing the nicotine composition formed from the liquidtobacco extract of the present invention may be used in conjunction withany suitable aerosol-generating device comprising a housing configuredto receive at least a portion of the cartridge. The aerosol-generatingdevice may comprise a battery and control electronics.

An embodiment of the present invention will now be further described, byway of example only.

COMPARATIVE EXAMPLE

In a method according to the first aspect of the present invention, atobacco material was cut to form tobacco shreds having maximumdimensions of 2.5 millimetres by 2.5 millimetres and the tobacco shredswere loaded into an extraction chamber, without compression. The tobaccomaterial was sprayed with an aqueous solution of potassium carbonate toprovide alkalised tobacco material having a pH of 9.5. The alkalisedtobacco material was heated within the extraction chamber to atemperature of 140 degrees Celsius for a period of 120 minutes. Duringheating, a flow of nitrogen was passed through the extraction chamber ata flow rate of about 20 litres per minute. The tobacco flow rate was 30kg per hour and the extraction chamber was rotated at a speed of 1 rpmin order to circulate the tobacco.

The volatile compounds released from the tobacco material during theheating step were collected by condensation at 0 degrees and added to aliquid solvent of propylene glycol.

The Nicotine Composition 1 shown in the table below is a liquid tobaccoextract obtained directly from the extraction process according to thefirst aspect of the present invention, with the alkaline treatment stepcarried out prior to heating.

In a second, comparative extraction method, the tobacco material wasextracted under the same conditions as described above, except that thealkaline treatment step was omitted. The second extraction method wastherefore not according to the present invention. The NicotineComposition 2 shown in the table below is a liquid tobacco extractobtained directly from this second extraction method.

Each of the nicotine compositions was analysed to measure the nicotinecontent and the nicotine yield was calculated based on the total dryweight of the tobacco material. The extraction yield of certain flavourcompounds was also measured. The results of this analysis are shown inthe table below:

Nicotine Nicotine Composition 1 Composition 2 Nicotine extraction yield(g/kg 13.3 1.6 of dry tobacco) 2,3-diethyl-5-methylpyrazine 10.5 1.3extraction yield (μg/kg of dry tobacco) 2-ethyl-3,5-dimethylpyrazine 15312 extraction yield (μg/kg of dry tobacco)

As clearly shown in the table above, the inclusion of the alkalinetreatment step in the method according to the first aspect of theinvention provides a significant increase in the nicotine extractionyield compared to the methods in which the alkaline treatment step isomitted. As also shown in the table above, the inclusion of the alkalinetreatment step provides a significantly improved extraction yield forcertain pyrazine flavour compounds, including2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine.

1.-14. (canceled)
 15. A method of producing a liquid tobacco extract,the method comprising the steps of: preparing a tobacco material;applying an alkaline solution to the tobacco material to produce analkalised tobacco material; heating the alkalised tobacco material at anextraction temperature of between 100 degrees Celsius and 160 degreesCelsius for at least 30 minutes, wherein the alkalised tobacco materialis heated in a flow of inert gas or in a flow of a combination of aninert gas with water or steam, and wherein a water content of thealkalised tobacco material, prior to the heating step, is between 10percent by weight and 20 percent by weight; condensing volatilecompounds released from the alkalised tobacco material during theheating step and collecting condensate of the volatile compounds; andforming a liquid tobacco extract comprising the condensate of thevolatile compounds.
 16. A method of producing a liquid tobacco extract,the method comprising the steps of: preparing a tobacco material;heating the tobacco material at an extraction temperature of between 100degrees Celsius and 160 degrees Celsius for at least 90 minutes;collecting volatile compounds released from the tobacco material duringthe heating step; forming a first liquid tobacco extract comprising thecollected volatile compounds from the tobacco material; applying analkaline solution to the residual tobacco material from the heating stepto produce an alkalised tobacco material; heating the alkalised tobaccomaterial at an extraction temperature of between 100 degrees Celsius and160 degrees Celsius; collecting volatile compounds released from thealkalised tobacco material during the heating step; and forming a secondliquid tobacco extract comprising the collected volatile compounds fromthe alkalised tobacco material.
 17. The method according to claim 16,further comprising the step of combining the first liquid tobaccoextract and the second liquid tobacco extract.
 18. The method accordingto claim 16, further comprising the step of isolating nicotine from thesecond liquid tobacco extract and combining at least a portion of theisolated nicotine from the second liquid tobacco extract with the firstliquid tobacco extract.
 19. The method according to claim 16, whereinthe tobacco material is heated in a flow of inert gas during at leastone of the heating steps.
 20. The method according to claim 15, whereina pH of the alkalised tobacco material is water is at least 8.5.
 21. Themethod according to claim 15, wherein a pH of the alkalised tobaccomaterial is water is at least 9.0.
 22. The method according to claim 16,wherein a pH of the alkalised tobacco material is water is at least 8.5.23. The method according to claim 16, wherein a pH of the alkalisedtobacco material is water is at least 9.0.
 24. The method according toclaim 15, wherein the alkaline solution is sprayed onto the tobaccomaterial, and wherein the tobacco material is continuously agitatedduring the spraying.
 25. The method according to claim 16, wherein thealkaline solution is sprayed onto the tobacco material, and wherein thetobacco material is continuously agitated during the spraying.
 26. Themethod according to claim 15, wherein the alkaline solution is anaqueous solution of potassium carbonate.
 27. The method according toclaim 16, wherein the water content of the alkalised tobacco materialprior to the heating step is between 10 percent and 20 percent byweight.
 28. The method according to claim 15, wherein an amount ofnicotine extracted from the alkalised tobacco material corresponds to atleast 10 grams per kg of dry tobacco material.
 29. The method accordingto claim 15, wherein the alkalised tobacco material is heated at anextraction temperature of between 135 degrees Celsius and 150 degreesCelsius.
 30. The method according to claim 15, further comprising thestep of spraying atomised water into an extraction chamber during theheating step.
 31. The method according to claim 16, further comprisingthe step of spraying atomised water into an extraction chamber duringthe heating steps.
 32. The method according to claim 15, furthercomprising the step of drying or concentrating the collected condensateof the volatile compounds.
 33. The method according to claim 16, furthercomprising the step of drying or concentrating the collected volatilecompounds.
 34. A liquid tobacco extract produced by the method accordingto claim 15.